Suspension for loudspeaker

ABSTRACT

A loudspeaker in which a diaphragm is supported at its marginal edge on a frame by means of a suspension which consists of an annular, hollow member of rubber-like elastic material having a substantially circular shape in cross section, which is connected at its inside periphery to said marginal edge of the diaphragm and at its outside periphery to said frame. A method for making the annular suspension member of rubber-like elastic material which comprises continuously extruding a hollow tube having a substantially circular cross section of the rubber-like elastic material in a helical form having a predetermined diameter, and then cutting the helically extruded hollow tube to form annular suspension members successively.

United States Patent Sotome [54] SUSPENSION FOR LOUDSPEAKER [72]Inventor: Hiromi Sotome, 7-5, Nakazawa-cho,

l-lamamatsu-shi, Shizuoka, Japan 22 Filed: Feb. 8, 1971 [21] Appl.No.:113,335

30 Foreign Application Priority um Feb. 13, 1970 Japan ..45/11985 Feb.13, 1970 Japan ..45/11986 [52] US. Cl. ..181/32 R, 181/31 R [51] Int. Cl..G10k 13/00, H04r 7/00 [58] FieldofSearch ..181/32 R, 31 R, 24

[56] References Cited I UNITED STATES PATENTS 1,454,913 5/ 1923Tigerstedt ..181/32 R 1,708,943 4/1929 Goodrum ..181/32 R 1,744,032l/1930 Baldwin ..181/32 R [151- 3,684,052 1 Aug. 15,1972

Primary Examiner-Stephen J. Tomsky Attorney-Henry T. Burke, RobertScobey, Robert S. Dunham, P. E. l-lenninger, Lester W. Clark, Gerald W.Grifi'm, Thomas F. Moran, R. Bradlee Boa], Christopher C. Dunham andJohn F Scully ABSTRACT A loudspeaker in which a diaphragm is'supportedat its marginal edge on a frame by means of a suspension which consistsof an annular, hollow member of rubber-like elastic material having asubstantially circular shape in cross section, which is connected at itsinside periphery to said marginal edge of the diaphragm and at itsoutside periphery to said frame. A method for making the annularsuspension member of rubber-like elastic material which comprisescontinuously extruding a hollow tube having a substantially circularcross section of the rubber-like elastic material in a helical formhaving a predetermined diameter, and then cutting the helically extrudedhollow tube to form annular suspension members successively.

3 Claims, 14 Drawing Figures PATENTED 1 5 i972 3.684.052

sum 1 nr 4 INVENTOR ////?0 M/ 0 70/145 BY #WJTM ATTORNEY 1 SUSPENSIONFOR LOUDSPEAKER BACKGROUND OF THE INVENTION The present inventionrelates to an improvement in a suspension or edge portion of a diaphragmof a loudspeaker and a method for making same.

I-Ieretofore, the suspension or edge portion of a diaphragm of aloudspeaker has been usually made of fabric material impregnated withphenol or urethane resin, non-woven fabric or rubber, which is formed ina corrugated or semi-curcular shape in cross section. In theconventional construction of the suspension, however, if it is so formedas to in crease its compliance in order to lower the minimum resonancefrequency of the loudspeaker, the formal stability of the edge portionof the diaphragm is reduced and the durability and strength thereof isalso reduced, so that it is susceptible to influence of difference inair pressure between front and rear sides of the diaphragm. Moreover, inthe conventional construction, the suspension must be formed one by one,so that its productivity is relatively low.

SUMMARY OF THE INVENTION It is a general object of the present inventionto eliminate the defects in the conventional construction of thesuspension of the loudspeaker.

It is an object of the present invention to provide a suspension of aloudspeaker which has an increased compliance and an increased formalstability, and a method of making such suspension.

It is another object of the present invention to provide a suspension ofa loudspeaker which is superior in durability and weather-resistantproperty and which is insusceptible to change due to aging andtemperature change and a method of making such suspension.

It is another object of the present invention to provide a suspension ofa loudspeaker which acts to vibrate in completely symmetric mode forwardand backward, thereby providing a loudspeaker with superiorcharacteristics.

It is a-further object of the present invention to provide a method forproducing a suspension of a loudspeaker at a high rate.

In accordance with an aspect of the present invention there is provideda suspension for supporting a marginal edge of a diaphragm on a frame ofa loudspeaker, comprising an annular hollow member of rubber-likeelastic material having a substantially circular cross section, which isconnected at its inside periphery to said marginal edge of the diaphragmand at its outside periphery to said frame.

In accordance with another aspect of the present invention there isprovided a method of making such suspension member, comprisingcontinuously extruding a hollow tube having a substantially circularcross section of the rubber-like elastic material into a form of a helixhaving a predetermined diameter, and then cutting the helically extrudedhollow tube to form an- I nular suspension members successively.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of aloudspeaker, showing an embodiment of the present invention;

FIG. 2 is a perspective view of a part of a suspension member of theloudspeaker as shown in FIG. 1;

FIG. 3 is a plan view of a part of the suspension member;

FIG. 4 is a sectional view of a part of loudspeaker, showing anotherembodiment of the present invention;

FIG. 5 is a schematic view illustrating a section of the suspensionmember shown in FIG. 4;

FIGS. 6 and 7 are sectional views, similar to FIG. 4, showing the otherembodiments, respectively;

FIGS. 8 and 9 are sectional views showing the modified forms of thesuspension member, respectivey;

FIG. 10 is a sectional view showing another embodiment of the invention;

FIG. 11 is a plan view showing a half of the loudspeaker shown in FIG.10;

FIG. 12 is a sectional view showing a modified form of the loudspeakershown in FIG. 10;

FIG. 13 is a schematic sectional view showing an apparatus for producingthe suspension member according to the present invention; and

FIG. 14 is a plan view of the same.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, the invention will beexplained with reference to the drawings which illustrate severalembodiments of the present invention.

The loudspeaker shown in FIG. I includes a diaphragm 1, a frame 2, avoice coil 3 supported at the center of the rear side of said diaphragm,a magnetic circuit 4 and a damper 5. The diaphragm 1 is supported at themarginal edge thereof on the frame 2 by means of an annular hollowsuspension member 6 having a substantially circular shape in crosssection. In the embodiment as shown in FIG. 1, the suspension member 6is integrally formed with an inside peripheral flange 7, to which themarginal edge of the diaphragm is adhesively fixed, and an outsideperipheral flange 8, which is adhesively fixed to the frame 2. Thesuspension member 6 is made of rubber-like elastic material, such asnatural rubber, synthetic rubber or foamed rubber such as foamedneoprene rubber or the like. The annular suspension member may be formedby extrusion molding of rubber-like elastic material. It may be eithermolded into an annular form at the time of extrusion, or it may beinitially molded into a straight tube, which is then curved as it isassembled onto the marginal edge of the diaphragm. In the latter case,radial slits 9 may be cut in the outside peripheral flange 8 tofacilitate to bend the straight extruded tube into the annular form.

FIG. 4 illustrates another embodiment of the invention, in which anannular suspension member 16 of substantially circular form in crosssection is formed with I an inside peripheral groove 17 which receives amarginal edge of a diaphragm and an outside peripheral flange l8adhesively fixed to a frame 2. The suspension member may be formed froma straight extruded tube, where said member may preferably has a crosssectional shape as shown in FIG. 5 in which the horizontal diameter a isslightly longer than the vertical diameter b and-the peripheral groove17 has outwardly tapered surfaces including an angle 0 a. When thestraight extruded tube is curved around the marginal edge of thediaphragm the cross sectional shape as shown in FIG. 5 is deformed intoa true circular form as shown in FIG. 4 and becomes to firmly grip saidmarginal edge of the diaphragm 1.

FIGS. 6 and 7 illustrate other two forms of the present invention. FIG.6 shows an annular suspension member 26 which is formed with an inside.peripheral flange 27 to which a marginal edge of a diaphragm 1 is fixedand an outside peripheral groove 28 which receives a flange 29 of aframe 2. FIG. 7 shows an annular suspension member 36 which is formedwith an inside peripheral groove 37 which receives a marginal edge of adiaphragm 1 and an outside peripheral groove 38 which receives a flange39 of a frame 2.

FIGS. 8 and 9 illustrate further modified forms of the suspension. FIG.8 shows an annular suspension member 46, which is similar to that shownin FIG. 4, except that the thickness is gradually increased from minimumthickness at the inside periphery 46 which receives larger vibration tomaximum thickness at the outside periphery 46" which receives smallervibration. FIG. 9 shows an annular suspension member 56, which issimilar to that shown in FIG. 4, except that a bridge portion 57 isintegrally formed therein to reinforce the suspension member and absortthe vibration thereof.

Any of the embodiments explained above meet the objects of the presentinventiin, but these embodiments may find some difficulty in centeringthe voice coil of the loudspeaker in the magnetic gap of the magneticcircuit owing to the fact that there is no clearance between thesuspension member fixed around the diaphragm and the inside periphery ofthe frame. Such a difficulty can be avoided by providing an additionalattaching ring around the annular suspension member of rubber-likeelastic material.

FIGS. 10 and 11 illustrate an embodiment of the invention including suchadditional attaching ring. This embodiment comprises a diaphragm 61, aframe 62, a voice coil 63, a magnetic circuit 64, a damper 65 and asuspension member 66. The suspension member 66 is provided with aninside peripheral groove 67, which receives a marginal edge of thediaphragm 61, and an outside peripheral groove 68 to which an annularattaching ring 69 is fitted and fixed. The attaching ring 69 is made ofsolid material, such as aluminum, iron, brass, hard plastics or thelike, and it is fixed on the frame such as by set screw or adhesive,with an adjusting clearance 70 between the outside periphery and theinside periphery of the frame.

FIG. 12 shows a further embodiment in which an annular suspension member76 has an inside peripheral groove 77, to which a marginal edge of adiaphragm 71 is fitted, and an outside peripheral flange 78, and anattaching ring 79 has an inside peripheral groove 80 into which theoutside peripheral flange 78 is fixed. The attaching ring 79 is fixed ona frame 72.

The loudspeaker as shown in FIGS. 10 and 12 is assembled by adhesivelyconnecting the diaphragm, the suspension member and the attaching ringtogether, attaching the voice coil to the diaphragm and then fixing theattaching ring on the frame by means of set screws, adhesives or thelike while centering the voice coil within the gap of said magneticcircuit using a suitable It will be understood from the abovedescriptions that a suspension member, which is of circular shape incross section, has an increased formal stability, so that the hardnessand the thickness of the suspension member can be reduced, compared withthe conventional construction of the edge portion of the diaphragm,whereby the compliance thereof can be increased to ideally high value.Because the suspension member has a symmetric shape in cross section,harmonic distortion could not be produced by the asymmetric vibration ofthe edge portion of the diaphragm. The air contained in the tubularsuspension member serves to suppress such vibration of the suspensionthat produces the variation of capacity in the suspension member, sothat the self-vibration of the suspension which would adversely afiectthe vibration of the diaphragm is suppressed. The suspension member,which has relatively high strength against the vibration of air at thefront and rear sides of the diaphragm, cannot produce distortion in thefrequency characteristics under the influence of the air vibration. Thesuspension member is superior not only in its fonnal stability but inits durability and weather-resistant property in view of the materialused for said member. The superior member, which has a circular section,is insusceptible to change due to aging and temperature change and keepsits shape-for a long period. This member can be produced very easily andcontinuously with low cost, by the extrusion molding. In theconstruction of the suspension member including the attaching ring fixedtherearound, the loudspeaker can be assembled easily with high accuracy.

.The above suspension member may be initially molded in the form of astraight extruded tube, which is then bent into an annular form aroundthe diaphragm, as explained above. However, it ispreferable to mold thesuspension member in an annular form at the time of extrusion thereof.

The present invention intends to provide a method for molding thesuspension member in the annular form by continuously extruding a tubeof rubber-like elastic material in a helical form and then cutting thehelical tube successively to form the annular suspension members.

FIGS. 13 and 14 illustrate an apparatus for carrying out such method,which comprises a tank 81 containing rubber-like elastic material 82, ahelical feeder 83 provided at the bottom of said tank, an electric motor84 for driving said feeder,a curved extruding nozzle 85 for helicallyextruding the material and a guide 86 for guiding the extruded material87 in the helical form. The helicoid has a diameter substantially equalto that of the final product suspension member to be mounted in aloudspeaker. The guide 86 has a plurality of guiding rollers 88projecting radially inward thereof, and the extruded material 87progressively descends in the guide in the helical form, while it isheated to be cured. The extruded material leaving the guide 86 issuccessively cut into annular suspension members. The annular memberthus formed is adhesively fixed around the diaphragm.

When the suspension member is initially formed in an annular form, whichis easily adapted around the diaphragm, no deformation of the suspensionmember may be caused at the time of attaching said suspension memberaround the diaphragm.

Iclaim:

1. A suspension for supporting a marginal edge of a diaphragm on a frameof a loudspeaker, comprising an annular, hollow member of elasticmaterial having a substantially circular shape in cross section, saidmarginal edge of the diaphragm and at its outside periphery to saidframe.

2. A suspension for supporting a marginal edge of a diaphragm on a frameof a loudspeaker, comprising an member being connected at its insideperiphery to said 5 annular, hollow member of elastic material having asubstantially circular shape in cross section, said member beingconnected at its inside periphery to said marginal edge of thediaphragm, and an attaching ring

1. A suspension for supporting a marginal edge of a diaphragm on a frameof a loudspeaker, comprising an annular, hollow member of elasticmaterial having a substantially circular shape in cross section, saidmember being connected at its inside periphery to said marginal edge ofthe diaphragm and at its outside periphery to said frame.
 2. Asuspension for supporting a marginal edge of a diaphragm on a frame of aloudspeaker, comprising an annular, hollow member of elastic materialhaving a substantially circular shape in cross section, said memberbeing connected at its inside periphery to said marginal edge of thediaphragm, and an attaching ring of solid material fixed at its insideto an outside periphery of said annular member and at its outside tosaid frame.
 3. A loudspeaker comprising a diaphragm, a frame, a voicecoil supported at the rear side of said diaphragm, a magnetic circuitsupported by said frame for driving said voice coil, and an annularhollow suspension member of elastic material having a circular form incross section, said suspension member being connected at its insideperiphery to a marginal edge of said diaphragm and at its outsideperiphery to said frame.